Composite plastic bearing and method for making the same

ABSTRACT

The invention contemplates an improved composite plastic sliding bearing or bearing element, and method and apparatus for making the same, wherein a fabric liner at a generally tubular bearing interface is backed by a particular reinforcement of tensed flexible strands which are embedded in a hard mass of bonding material. High radial-compression load on the bearing is stoutly resisted by the reinforcement which comprises interlaced winding traverses at different helical-advance angles.

United States Patent Matt et a1.

[54] COMPOSITE PLASTIC BEARING AND METHOD FOR MAKING THE SALE [72]Inventors: Richard .1. Matt, Simsbury; Thomas P. Rolland, Bristol, bothof Conn.

[73] Assignee: Textron Inc., Providence, R1.

[22] Filed: Dec. 1, 1970 21 Appl. No.: 94,091

[52] U.S. Cl. ..308/238, 87/1, 138/144, 156/195 [51] Int. Cl. ..Fl6c33/14 [58] Field of Search ..308/238; 156/184, 190, 195; 87/1; 138/144,129

[56] References Cited UNITED STATES PATENTS 3,604,463 9/1971 McLarty138/144 3,635,256 1/1972 McLarty ..308/238 X 3,533,668 10/1970 Tunis..308/238 2,953,418 9/1960 Runton et a1. ..308/238 2,862,283 12/1958Rasero ..308/238 3,000,076 9/1961 Runton et a1. ..308/238 3,053,5929/1962 Runton et a1. ..308/238 3,328,100 6/1967 Spokes et al ..308/238[151 3,692,375 51 Sept. 19,1972

1,900,298 3/1933 Morris ..308/238 X 2,783,173 2/1957 Walker et a1...156/190 2,815,043 12/1957 Kleiner et al. ..156/195 X 2,932,597 4/1960St. John et al. ..156/190 3,294,609 12/1966 Foll ..156/190 OTHERPUBLICATIONS Kirk-Othmer, Ency. of Chem. Tech, 2d Ed., 1968, pg. 29 etal.

Primary Examiner-Martin P. Schwadron Assistant Examiner-Barry GrossmanAttorney-Sandoe, l-lopgood and Calimafde ABS'I RACT The inventioncontemplates an improved composite plastic sliding bearing or bearingelement, and method and apparatus for making the same, wherein a fabricliner at a generally tubular bearing interface is backed by a particularreinforcement of tensed flexible strands which are embedded in a hardmass of bonding material. High radial-compression load on the bearing isstoutly resisted by the reinforcement which comprises interlaced windingtraverses at different helical-advance angles.

19 Claims, 6 Drawing Figures COMPOSITE PLASTIC BEARING AND METHOD FORMAKING THE SAME This invention relates to fabric-lined hearings orbearing elements and to methods of making the same. More particularly,the invention is concerned with such hearings in which the lining and acircumferential envelopment of filamentary reinforcement, or backing,are embedded in and bonded to a hard resinous bonding material. Thebearings or bearing elements of the invention involve sliding rotationalsurfaces at an interface, which may or may not be cylindrical and whichis therefore termed generally tubular of generally cylindrical.

Techniques are known for producing composite plastic bearings withlow-friction fabric liners, and in journal-bearing application of suchbearings it is convenient to form the bearing on a cylindrical mandrelwhich can be removed, and then reused, to make more bearings or bearingelements. Such techniques are disclosed, for example, in U.S. Pat No.3,507,022. Such techniques have, however, ignored the 7 problemspresented by high radially directed compressional loading, and they havenot provided the simplicity needed for mass-production of high-capacity,high-quality products, at relatively low cost. For example, in bearingswherein woven fabric is relied upon for reinforcement of the liner,there is a tendency to undergo deformation under load; that is, theliner tends to cold flow and be displaced (hydrodynamically) out theends of the bearing, thereby resulting in excessive clearance and wear.

It is, accordingly, an object of the invention to provide an improvedarticle of the character indicated, as well as an improved method andapparatus for making the same.

Another object is to achieve the above object for an inherentlyhigh-capacity bearing, at relatively low cost.

A further object is to provide a bearing element, and a method andapparatus for making the same, wherein an inherent capacity exists forgreater life, for a given load utilization.

A specific object is to achieve the foregoing objects with an article,method and apparatus lending themselves to economy in the use oflow-friction liner material.

Another specific object is to provide bearing elements of the characterindicated, having improved resistance to distortion under load.

A further specific object is to achieve the stated objects withapparatus and a method lending themselves to selective manufacture of aplurality of different sizes and types of bearing.

Other objects and various further features of novelty and invention willbe pointed out or will occur to those skilled in the art from a readingof the following specification, in conjunction with the accompanyingdrawings. In said drawings, which show, for illustrative purposes only,preferred forms and methods of the invention:

FIG. 1 is a view in side elevation, partly broken-away and in verticalsection to show a bearing element of the invention;

FIG. 2 is a fragmentary vertical sectional view to show a modifiedbearing element;

FIG. 3 is a simplified and schematic diagram of apparatus of theinvention, for making bearing elements, as in FIGS. 1 and 2; and

FIGS. 4, 5 and 6 are similar fragmentary views in elevation toillustrate different steps in making bearing of the invention.

According to the invention, an improved composite plastic slidingbearing or bearing element, and method and apparatus for making thesame, are provided wherein a fabric liner at a generally tubular bearinginterface is backed by a particular reinforcement of tensed flexiblestrands which are embedded in a hard mass of bonding material. Highradial-compression load on the bearing is stoutly resisted by thereinforcement which comprises interlaced winding traverses at differenthelical-advance angles.

Referring to FIG. 1 of the drawings, the invention is shown inapplication to a journal bearing element or sleeve 10 comprising afabric liner 1 1 and one or more layers 12-13 of reinforced backing,circumferentially surrounding and retaining the liner 11. The variouslayers 11 12-13 may be embedded and bonded in a single hard resinmaterial, such as an epoxy, and therefore the same plasticcross-hatching is employed to show the section for all layers. The boreof the liner 11 has rotational or other sliding fit to a shaft 14; theinner concave surface of the liner 11 thus defines the bearinginterface.

The liner fabric 11 may be of various forms. Thus, it may be a wovenlow-friction fabric as in said U.S. Pat. No. 3,507,022, or it may be astretched low-friction braided fabric or sock as disclosed in Van Dorn,et al. application (Attorney File 025), filed on even date herewith. Itmay also be a knitted fabric, or it may be the result of helicallywinding low-friction and bondable fibers or strands in a first directionof traverse, with an overlapping return traverse of the same kind ofwinding, as will later be more clear. It suffices to say that for alow-friction liner fabric 11, the mix of fibers, filaments, strands oryarns is preferably a polyfluorocarbon such as Teflon, and a polyamidesuch as Nomex, with possibly a small component of Dacron, in view of theshrinking capabilities ofthe latter under the curing conditions forcertain impregnating resinous bonding materials.

The backing for liner 11 is shown as Backing A (layer 12) and Backing B(layer 13) in order to permit separate identification, although the sameflexible reinforcing strands, filaments or yarns may be used in bothlayers 12-13. Glass fiber is preferred as such reinforcing material, andin accordance with the invention the various layers 12-13 differ fromeach other in the magnitude of helical-advance angle which characterizesthe development of reinforcing material in the respective layers 12-13.The different helical-advance angles at particular layers are selectedfor achieving a primarily radially compressive or circumferentiallyretaining reinforcement of the one hand, or a primarily axiallyretaining or end-wall reinforcement on the other hand. Choice of theorder and nature of these angles and layers will depend inter alia uponthe type of liner and on the proportions of the cross-section of theparticular bearing element. Generally, however, we prefer to introducethe large-angle helix winding as the initial back-up winding, or atleast as close as practical to the liner 11, for reasons of providinggreatest axial retention of liner fiber at the bearing interface.

Thus, for example, for a liner fabric 11 which is woven fabric on thebias (i.e., oriented on the bias, in

the sense of the circumferential wrap), or other biased forms (such asbraided fabric, or high-pitch helical wraps), the first backing layer 12is primarily circumferential in nature and is relatively thin; thisentails but a few traverses of a relatively small or low-angle helicaladvance, thereby providing maximum cross-over of individual strands ofthe bias-oriented liner material. Having thus positioned the linermaterial, the second backing layer 13 is preferably characterized bysuch a large angle of helical advance of reinforcing strands that thereis (a) maximum cross-over of individual strands of the layer 12 and (b)a substantial component of axially retaining action, and successivecourses of winding the reinforcing material are preferably phased formaximum interlace, for greater stabilizing effect.

By the same token, for a liner fabric 11 in which orthogonally coursedthreads are oriented in the circumferential and longitudinal directions,respectively, the adjacent backing layer 12 is preferably characterizedby a relatively large helical-advance angle, followed in alternation bysuccessive further layers of interlaced small and large advance-anglehelices. Such a development is suggested in FIG. 2, wherein the legendBackings A identifies plural layers of low-angle helix reinforcement,radially interlaced with Backings B of large-angle helix reinforcement.

In making bearing elements as in FIGS. 1 or 2, a core element or mandrelis selected, with outer convex contour as desired for the bearinginterface. For FIG. 1, the shaft 14, of radius R may be considered asthe core or mandrel; it may be characterized by a low-friction ornon-bondable surface or it may be coated with a wax, silicone or otherparting agent for the same purpose. The liner 11 is next applied, bywinding, circumferential wrapping, or axial stretching, depending on itsnature; this develops to a new radius R,. Liner 11 may be preimpregnatedor wetted with the hardenable bonding material, as after wringing-outand drying to the B-stage (pliable) of the bendable material; however,we prefer to apply the bondable material in its liquid phase just priorto, in the course of, or just after applying liner material to the coreor mandrel. The reinforcing layers are then developed as windings(different helix angles) of the same reinforcing threads or strands, thewinding being wetted with more liquidphase bonding material, in thecourse of winding. As shown, layer 12 develops to a radius R and theouter layer 13 is developed to a radius R, which exceeds that (R desiredin the finished product. The liquid-impregnated wound assemble (radius Ris then preferably enveloped, as with a foil wrap, to retain the liquidof the bondable material, and for convenience in handling in the curingenvironment. Once cured to hardness, the foil wrap and the outer surfaceare removed, in turning, grinding or other finishing operations toradius R The axial ends are also cut and faced to desired dimensions andprofile, as after removal from the core or mandrel.

F IG. 3 illustrates apparatus that is particularly useful in producing along sleeve from which separate bearing elements may be cut. The machineapplies the reinforcement strands in interlaced layers, as desired, andwith preselected conditions determining the different angles of helicaladvance. The machine uses a frame which is schematically shown byvarious shaded regions of reference thereto, as at 20 for a rotarybearing 21. The long bearing sleeve is developed on a mandrel 22,revolubly supported by means 21 and connected for drive by means 23.Clamp means 19 at one or both ends of the mandrel provides anchoringend-reference for the sock or other material of the liner ll.Filamentsupply means 24 is provided with a plurality of upstandingsupports or spindles for individual yarn bobbins 25 for the reinforcingstrands or yarns, and guides such as eyes or rings 26-27 position theindividual strands, as necessary, as to present a closely adjacentlongitudinally spaced array, for plural pay-out in developing thehelical wrap; preferably, the pay-out is under tension, and theschematic showing at eyes 26 will be understood as illustrativelyincorporating a tension-drag feature, as produced by a spring-loadedshoe constituting part of the structure of each pay-out eye 26.

The filament-supply means 24 may be fixed, and the rotating mandrel maybe traversed to the right and left to produce such wrap; however, in theform shown, it is the mandrel 22 which is held while the filament-supplymeans 24 is a traversed slide or carriage. For this purpose, guide means28 is frame-referenced at 29 and assures that motion of thefilament-supply means will be parallel to the rotary axis of mandrel 22.A lead-screw 30 schematically depicts the means for traverse-feeding thefilament-supply means 24. Screw 30 has threaded engagement with afollower nut (not shown) forming part of the carriage 24; a rotarythrust bearing 31 is shown as a means for establishing frame-referencedsupport of screw 30, and drive is from means 23, by way of change-gear32 and reversing-gear means 33. Thus, for a given drive at 23, and forgiven gear selections at 32-33, the carriage 24 will have a definitetraverse rate and direction, determining a particular helical angle a ofadvance of strand wrap, for a particular built--up diameter D of thepartially loaded mandrel. For the instant depicted in FIG. 3, the anglea is in the order of 45, and the clustered spread W of payedout andenwrapping reinforcing threads 34 substantially matches the helicaladvance lead per turn, thus assuring smooth, continuous longitudinalinterlace of the helices of the individual threads. Actually, the spreadW of the plural threads 34 is exaggerated, for clarity of drawing, andit will be appreciated that for the angle a of the indicated magnitude,the spread W will be but a fraction of the advance lead L per turn, asis apparent in FIG. 4, to be later discussed. However, for a differentgear selection at 32, wherein lead-screw rotation is at a slower pace,the spread W may substantially match the lead L because the angle a ofhelical advance will have been so materially reduced that thereinforcing thread wrap is essentially or primarily circumferential;such a wrap has commenced, from leftto-right in FIG. 6 (at 50), to belater discussed.

The carriage 24 is shown further equipped with a bracket 35 forpositioning a reservoir and brush applicator 36 in wetting contact withthe instantaneous path of wrap on the mandrel; reservoir 36 will beunderstood to contain and dispense a supply of liquidphase bondingmaterial. Alternatively, we may use a resin cup through which theindividual threads are drawn, to wet the threads with bonding materialjust prior to wrapping on the mandrel.

The remainder of FIG. 3 is suggestive of automatic operation inaccordance with the invention. Framemounted limit switches 37-38 arepositioned for coaction with a lug 39 on the carriage 24, to determinethe respective traverse limits. Each of these switches has a connectionto reversing-control means 40, which may include a flip-flop with acontrol connection to the reversing-gear means 33. Thus, upon operationof switch 37, control 40 is shifted from its first to its second state,to initiate at 33 a reversed drive of the lead-screw 30 (withoutchanging the gear ratio at 32); similarly, upon attainment of the othertraverse limit, the switch 38 is operated, to shift control 40 back toits first state, and to again reverse gear means 33, back to thedirection for right-to-left traverse feed.

In addition to the indicated automatic reversal of traverse, the circuitof FIG. 3 is seen to include a counter 41 for the number of traversesneeded in Backing A" and a similar counter 42 for the number oftraverses needed in Backing B; manual means 41' and 42' will beunderstood to afford selective determination of such numbers. Each ofcounters 41-42 has an input connection 43 from the limit switch 37,thereby enabling a one-count counter index for each completed traversecycle (to the right, and return to the left). In that part of theoperation in which Backing A is being generated, the counter 41 willhave been enabled (as will later be clear), and the count proceeds asthe winding builds to the extent selected by adjustment at 41. Uponattaining this extent, counter 41 produces an output signal to changethe state of switch means 45, thereby (a) controlling an actuator 46 forshifting the gear-change means 32 to a new gear ratio, appropriate forgeneration of the helical-advance angle desired in Backing B, and (b)imparting a disabling pulse at 44 to counter 41; an interlock connection47 between counters 41-42 assures the enabling of one counter 42 (41)upon the disabling of the other 41 (42). The count and winding forBacking B" can now proceed, without interrupting the continuous rotationof the mandrel and payout of wrapping strands 34. When BAcking B" hasbuilt to the desired number of traverse counts (preselected at 42'),switch means 45 is operated to control actuator 48 for gear shift at 32back to the ratio for further Backing A winding development; also, asignal at 49 disables counter 42 and, through interlock 47, reinstatesthe operative counting function at 41 for a Backing A" winding. Suchlayer development recycles until the desired full diameter (radius R isreached, whereupon the machine may be shut down manually, orautomatically, as by photocell detection of an interrupted light beam,in disconnect relation with the drive means 23 (see legend);alternatively, the shut-sown control may be a counter, operative toshut-off drive means 23 after completion of a preselected number ofwinding traverses.

FIGS. 4, 5 and 6 illustrate the pattern of winding development producedby the machine of FIG. 3. In FIG. 4, a first large helix-angle windinghas begun, with a strand spread W which is only a small fraction of thehelix lead L. The space between the applied strands of the firsttraverse should be filled by successive traverses, as by suitably spacedset-up placement of the limit switches 37-38. For example, if the helixangle is such that W approximates one-fourth of L, then switch 38 shouldbe so spaced from switch 37 as to represent a given number of full helixturns, plus one-eighth of a turn (45 of a helix turn). This means thateach successive traverse of the mandrel in a given direction (e.g., leftto right) will lay down strands 34 along a path adjacent to but notoverlapping the previous path. Legends for the second and thirdtraverses illustrate such phase shift for each traverse; and the fourthtraverse, of course, fills the one remaining swath space, to present theappearance shown in FIG. 5. In FIG. 6, it is assumed that thelarge-angle helix winding has been completed and that the pre-selectedcount limit has caused gear-shifting to the ratio for a circumferentialwinding (low helix angle); the winding 50 is shown proceeding at suchlow angle of helical advance.

It has been generally indicated that the fabric liner 11 may be theproduct of reversing-traverse winding, as produced by the machine ofFIG. 3. Thus, the above discussion of FIGS. 4 and 5 may be taken toapply for generation of the liner 11, the supply spools 25 beingprovided of course with yarn material or strands appropriate to thedesired composition at the bearing interface. For low-frictioninterface, each strand 34 may, for example, be a like combined mix ofTeflon, Nomex, and Dacron filaments; or adjacent strands may be ofdifiering composition, all to the end that the desired mix is availableat the interface. Having completed the four right and four lefttraverses needed to cover the mandrel (as in FIG. 4) and to impregnatethe resulting fabric liner 11, the reinforcing windings are developed aspreviously described; this may be accomplished b relocating thepartially wound mandrel on another FIG. 3 machine which is set up forwinding with reinforce material, or a second deck of carriage 24 (or asecond carriage 24) appropriately loaded with and for pay-out ofreinforce material may enable use of the same machine for all winding.

It will be seen that the invention meets the stated objects and providesa superior product at low cost. Great flexibility is afforded as to sizeand configuration of bearing element, and as to yarn or strandcomposition at the various layers. The liner strands may comprise aplurality of polyfluorocarbon filaments intertwined with filaments ofone or more resin bondable fibrous materials. The term polyfluorocarbonsincludes polymers and copolymers of ethylenically unsaturated fluorinecontaining monomers such as polytetrafluoroethylene, amylidine fluoride,chlorotufluoroethylene and hexafluoropropylene. The distinguishingcharacteristic of these polyfluorocarbon polymers and copolymers istheir low surface energy which gives these materials self-lubricatingproperties when in rubbing or sliding contact with hard materials suchas metal. Preferably the polyfluorocarbon is tetrafluoroethylene(Teflon). Such polyfluorocarbon fibers are resin bondable only withdifficulty; hence to provide a suitably rigid bearing liner they areusually intertwined with resin bondable fibers such as cotton, rayon,dacron, or any of the various nylons. Because of its strength,high-temperature nylon (Nomex) is particularly preferred; also, asindicated above, the Nomex does not materially degrade the low-frictionperformance attributable to the Teflon, and it assures that the Teflonwill be held in place. Use of etched Teflon yarn also improvesbondability and place-retention of the Teflon, a suitable such yarnbeing available in 400/ 16/3, where 400 is the denier, 16 is the numberof ends, and 3 is the number of twists per inch.

The hardenable bonding material may be an epoxy resin or a phenolic orthe like. The angle of helical advance will vary from one situation toanother, but generally it may be stated that the "circumferential wrapsinvolve helical lead angles in the range to 10, whereas the large-anglewraps involve helical lead angles in the range of 30 to 75. Byinterlacing the reverse-traversed laps of such windings, we have foundthat superior deformation resistance is imparted to the final product,regardless of the fractional amount of winding that is left, uponcut-off from a long cured sleeve.

In a typical example utilizing the invention, a plurality ofsleevebearing elements 10 is produced by generating and curing a longsleeve, with impregnated multiple windings, described as follows:

Long sleeve length: 40 inches Long sleeve built contour (R 0.618 inchMandrel radius (R,,); 0.500 inch Lining ll: 30 percent TFE, 70 percentNomex,

0.0 l 8 inch thick Backing A": 0.0l inch (one layer or five passes),

at 45 helix Backing B: 0.085 inch (two layers or four passes),

circumferential wrap Bonding material: epoxy, cured and thermallystabilized Finished bearing cut-off intervals: 10 inches Finishedbearing width; 0.5 inch to 10 inches, as

desired Finished bearing outer profile (R l.l 250/ 0.5625 inch While theinvention has been described in detail for the preferred bearingelements, methods and apparatus shown, it will be understood thatmodifications may be made without departure from the invention.

What is claimed is:

1. A bearing element of generally tubular configuration having concaveinner and convex outer surfaces substantially concentrically disposed,said bearing element comprising:

a. an inner liner formed of interlaced strands of yarn and having atubular configuration generally corresponding to that of the innersurface of said bearing, at least some of said strands comprising aplurality of low-friction filaments intertwined with filaments of atleast one resin-bondable fibrous material wherein said low-frictionfilament containing strands are so disposed that at least some of saidlow-friction filaments are exposed at said inner bearing surface; and

. a rigid concentric backing for said liner, the inner surface of saidbacking being bonded to the outer surface of said liner, said backingcomprising a cured hardenable resin having imbedded therein a pluralityof interlacingly wound resin-bondable reinforcing fiber layers whereinat least some of said layers are helically wound and wherein the helixangle of one of said helically wound layers is substantially differentfrom that of an adjacent other of said helically wound layers.

2. A bearing element in accordance with claim I wherein said reinforcingfiber layers comprise a layer of relatively small helix anglesubstantially coaxially in terlaced with a plurality of layers ofrelatively great helix angle.

3. A bearing element in accordance with claim I, wherein saidreinforcing fiber layers comprise a layer of relatively great helixangle substantially coaxially in terlaced with a plurality of layers ofrelatively small helix angle.

4. A bearing element in accordance with claim 1, wherein saidreinforcing fiber is glass fiber.

5. A bearing element in accordance with claim 1, wherein said resin isan epoxy resin.

6. A bearing element in accordance with claim I, wherein saidlow-friction filament is polytetrafluoroethylene.

7. A bearing element according to claim 6, wherein said low-frictionfilament is of the etched variety.

8. A bearing element in accordance with claim 1, wherein saidresin-bondable fibrous material is a polyamide.

9. A bearing element in accordance with claim I, wherein said polyamideis poly-E-caprolactam.

10. A bearing element in accordance with claim 1, in which said innerliner comprises a helical progression of plural strands ofresin-bondable material and of lowfriction material, characterized by atleast one direction of helical advance in which said plural strands arelocated at a fraction of the area of said surface and by an overlappingand opposite direction of helical advance in which remaining portions ofsaid plural strands are located at a remaining fraction of the area ofsaid surface.

11. The method of making a bearing element of generally tubularconfiguration and with concave inner and convex outer surfacessubstantially concentrically disposed, which method comprises selectinga hard elongated central core member with a convex outer surface of thesize and configuration desired for the inner surface of the bearingelement, circumferentially enveloping said core member with flexiblelow-friction fabric material, helically winding over said material aplurality of strands of a reinforcing material to whichhardenable-liquid bonding resin material is bondable, said windingcomprising a plurality of traverses of said core member in bothlongitudinal directions using substantially different helical-advanceangles on different traverses of said core member, said reinforcingmaterial and said fabric material being impregnated with said bondingmaterial, whereby fibers of the fabric material and of said reinforcingmaterial are embedded in hardenable material, and curing the hardenablematerial to hardness.

12. The method of making a plurality of bearing elements of generallytubular configuration and with concave inner and convex outer surfacessubstantially concentrically disposed, which method comprises selectinga mandrel of length exceeding the combined axial widths of the desiredplurality of bearing elements and of diameter matching the desired innerbearing surface, circumferentially enveloping said mandrel with flexiblelow-friction fabric material, helically winding over said material aplurality of strands of a reinforcing material to whichhardenable-liquid bonding resin material is bondable, said windingcomprising a plurality of traverses of said mandrel in both longitudinaldirections using substantially different helical-advance angles ondifferent traverses of said mandrel, said reinforcing material and saidfabric material being impregnated with said bonding material, wherebyfibers of the fabric material and of said reinforcing material areembedded in hardenable material, curing the hardenable material tohardness, and severing separate bearing elements by radial-plane cuttingof the hardened mass at substantially bearing-unit intervals.

13. The method of claim 12, in which said helical winding step isperformed by use of different helicaladvance angles on differenttraverses of said mandrel.

14. The method of claim 12, in which one of said helical-advance anglesis characterized by relatively small longitudinal advance per wrappedturn and in which the other of said helical-advance angles ischaracterized by a longitudinal advance per turn that is substantiallythe wrapped diameter of the turn.

15. The method of claim 12, in which one of said helical-advance anglesis so small as to effect substantially circumferential envelopment ofsaid fabric material, and in which the other of said helical-advanceangles is so large as to effect a substantial component of longitudinalelongation the envelopment of said fabric material.

16. The method of claim 15, in which successively built-up layers ofreinforcing material are comprised of groups of traverses at onehelical-advance angle interlaced with groups of traverses at the otherhelical-advance angle.

17. The method of claim 12, in which said strands are wound undertension.

18. The method of claim 12, in which said mandrel has anon-resin-bondable outer surface.

19. The method of claim 12, in which the plural rein forcing strands arein close longitudinally adjacent array as they are helically wound.

* l l l UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,692,375 Dated September 19 1972 lnventofls) RICHARD J. MATT, ET. AL.

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

In the drawing, in Figure 3, the rectangular box immediately above andto the left of threads "34" should be labelled with reference numberal36.

Signed and sealed this 13th day of August 1974.

(SEAL) Attest:

McCOY M. GIBSON, JR. C. MARSHALL DANN Attesting Officer Commissioner ofPatents ORM PO-l 050 (10-69) USCOMM'DC 60376-P69 9 [1.5. GOVERNMENTPRINTING OFFICE ISIQ 0-366-33.

1. A bearing element of generally tubular configuration having concaveinner and convex outer surfaces substantially concentrically disposed,said bearing element comprising: a. an inner liner formed of interlacedstrands of yarn and having a tubular configuration generallycorresponding to that of the inner surface of said bearing, at leastsome of said strands comprising a plurality of low-friction filamentsintertwined with filaments of at least one resin-bondable fibrousmaterial wherein said low-friction filament containing strands are sodisposed that at least some of said low-friction filaments are exposedat said inner bearing surface; and b. a rigid concentric backing forsaid liner, the inner surface of said backing being bonded to the outersurface of said liner, said backing comprising a cured hardenable resinhaving imbedded therein a plurality of interlacingly wound resinbondablereinforcing fiber layers wherein at least some of said layers arehelically wound and wherein the helix angle of one of said helicallywound layers is substantially different from that of an adjacent otherof said helically wound layers.
 2. A bearing element in accordance withclaim 1 wherein said reinforcing fiber layers comprise a layer ofrelatively small helix angle substantially coaxially interlaced with aplurality of layers of relatively great helix angle.
 3. A bearingelement in accordance with claim 1, wherein said reinforcing fiberlayers comprise a layer of relatively great helix angle substantiallycoaxially interlaced with a plurality of layers of relatively smallhelix angle.
 4. A bearing element in accordance with claim 1, whereinsaid reinforcing fiber is glass fiber.
 5. A bearing element inaccordance with claim 1, wherein said resin is an epoxy resin.
 6. Abearing element in accordance with claim 1, wherein said low-frictionfilament is polytetrafluoroethylene.
 7. A bearing element according toclaim 6, wherein said low-friction filament is of the etched variety. 8.A bearing element in accordance with claim 1, wherein saidresin-bondable fibrous material is a polyamide.
 9. A bearing element inaccordance with claim 1, wherein said polyamide is poly-E-caprolactam.10. A bearing element in accordance with claim 1, in which said innerliner comprises a helical progression of plural strands ofresin-bondable material and of low-friction material, characterized byat least one direction of helical advance in which said plural strandsare located at a fraction of the area of said surface and by anoverlapping and opposite direction of helical advance in which remainingportions of said plural strands are located at a remaining fraction ofthe area of said surface.
 11. The method of making a bearing element ofgenerally tubular configuration and with concave inner and convex outersurfaces substantially concentrically disposed, which method comprisesselecting a hard elongated central core member with a convex outersurface of the size and configuration desired for the inner surface ofthe bearing element, circumferentially enveloping said core member withflexible low-friction fabric material, helically winding over saidmaterial a plurality of strands of a reinforcing material to whichhardenable-liquid bonding resin material is bondable, said windingcomprising a plurality of traverses of said core member in bothlongitudinal directions using substantially different helical-advanceangles on different traverses of said core member, said reinforcingmaterial and said fabric material being impregnated with said bondingmaterial, whereby fibers of the fabric material and of said reinForcingmaterial are embedded in hardenable material, and curing the hardenablematerial to hardness.
 12. The method of making a plurality of bearingelements of generally tubular configuration and with concave inner andconvex outer surfaces substantially concentrically disposed, whichmethod comprises selecting a mandrel of length exceeding the combinedaxial widths of the desired plurality of bearing elements and ofdiameter matching the desired inner bearing surface, circumferentiallyenveloping said mandrel with flexible low-friction fabric material,helically winding over said material a plurality of strands of areinforcing material to which hardenable-liquid bonding resin materialis bondable, said winding comprising a plurality of traverses of saidmandrel in both longitudinal directions using substantially differenthelical-advance angles on different traverses of said mandrel, saidreinforcing material and said fabric material being impregnated withsaid bonding material, whereby fibers of the fabric material and of saidreinforcing material are embedded in hardenable material, curing thehardenable material to hardness, and severing separate bearing elementsby radial-plane cutting of the hardened mass at substantiallybearing-unit intervals.
 13. The method of claim 12, in which saidhelical winding step is performed by use of different helical-advanceangles on different traverses of said mandrel.
 14. The method of claim12, in which one of said helical-advance angles is characterized byrelatively small longitudinal advance per wrapped turn and in which theother of said helical-advance angles is characterized by a longitudinaladvance per turn that is substantially the wrapped diameter of the turn.15. The method of claim 12, in which one of said helical-advance anglesis so small as to effect substantially circumferential envelopment ofsaid fabric material, and in which the other of said helical-advanceangles is so large as to effect a substantial component of longitudinalelongation the envelopment of said fabric material.
 16. The method ofclaim 15, in which successively built-up layers of reinforcing materialare comprised of groups of traverses at one helical-advance angleinterlaced with groups of traverses at the other helical-advance angle.17. The method of claim 12, in which said strands are wound undertension.
 18. The method of claim 12, in which said mandrel has anon-resin-bondable outer surface.
 19. The method of claim 12, in whichthe plural reinforcing strands are in close longitudinally adjacentarray as they are helically wound.